1. Field of the Invention
The present invention relates to protection circuits for protecting electrical motors for example.
2. Description of the Prior Art
Electrical appliance protection circuits are known which incorporate reed relays as well as other relays havng contact sets which operate in response to direct currents applied to the winding of the relay and act as a circuit breaker for the appliance. Such relays cannot operate satisfactorily if supplied with an alternating current even when the alternating current is first rectified since the contacts will tend to open each time the current drops to zero level at the end of every half cycle. This results in vibrations which will reduce the service life of the circuit breakers. It is an object of the invention to provide an improved protection circuit for an electrical appliance.
It is a more particular object to provide a protection circuit for the protection of three-phase motors by detecting a possible phase interruption or an open-circuit condition of the motor, and then operating a circuit breaker to disconnect the motor from the supply.